The Boeing 737 is a short to medium range, single aisle, narrow body jet airliner. Originally developed as a shorter, lower-cost twin-engine airliner derived from Boeing's 707 and 727, the 737 has nine variants with the -600, -700, -800 and -900 currently in production.

Originally envisioned in 1964, the 737 first flew in 1967, [1] and entered airline service in February 1968. [1] [5] The 737 is Boeing's only single-aisle, narrow-body airliner currently in production, sometimes serving markets previously filled by 707, 727, 757, DC-9 and MD-80/90 airliners.

The 737 has been continuously manufactured by Boeing since 1967 with over 6,000 aircraft delivered and 2,000 orders yet to be fulfilled as of May 2009. [6] The 737 series is the most-ordered and most-produced jet airliner in history as of April 2009. [1] There are on average 1,250 737s airborne at any given time, with one departing or landing somewhere every five seconds on average. [7]

Boeing 737

Role:

Airliner

National Origin:

United States

Manufacturer:

Boeing Commercial Airplanes

First Flight:

April 9, 1967

Introduction:

February 10, 1968 with Lufthansa

Status:

Active

Primary Users:

Southwest Airlines, Ryanair, Continental Airlines, Alaska Airlines

Produced

1968 – Present

Number Built:

6,199 as of 31 October 2009 [1]

Variants:

737-100: US $32 million [2] - 737 NG: US $51.5-87 million (2008) [3][4]

Variants:

Boeing T-43, Boeing 737 Classic, Boeing 737 Next Generation

Development

Origins

Boeing had been studying short-haul jet aircraft designs and wanted to produce another aircraft to supplement the 727 on short and thin routes. [8] Preliminary design work began on 11 May 1964, [9] and Boeing's intense market research yielded plans for a 50 to 60 passenger airliner for routes 50 to 1,000 mi (80 to 1,610 km) long. [8] [10] Lufthansa became the launch customer on 19 February 1965, [11] with an order for 22 aircraft, worth $67 million [12] (1965, $190.28 million in 2008), after the airline reportedly received assurances from Boeing that the 737 project would not be cancelled. [13] Consultation with Lufthansa over the previous winter resulted in an increase in capacity to 100 seats. [11]

On April 5, 1965, Boeing announced an order by United Airlines for 40 737s. United wanted a slightly larger airplane than the original design; therefore, Boeing stretched the fuselage an extra 91 centimetres (36 in) ahead of, and 102 centimetres (40 in) behind the wing. [14] The longer version was designated 737-200, with the original short body aircraft becoming the 737-100. [15]

Detailed design work continued on both variants at the same time. Boeing was far behind its competitors when the 737 was launched, as rival aircraft BAC 1-11, Douglas DC-9, and Fokker F28 [12] were already into flight certification. To expedite development, Boeing utilized 60% of the structure and systems of the existing 727, most notably the fuselage cross section. This fuselage permitted six-abreast seating compared to the rival 1-11 and DC-9's five-abreast layout, [11] but the widened cross-section and short fuselage complicated the aerodynamics of the aft-mounted engines common with airliners of the time. As a result, engineers decided to mount the nacelles directly to the underside of the wings. The placement of this weight below the center of the aircraft also reduced stresses on the airframe, which allowed for a lighter wing, [16] and kept the engines low to the ground for easy ramp operations. [17] The engine chosen was the Pratt & Whitney JT8D-1 low-bypass ratio turbofan engine. [18] With the wing-mounted engines, Boeing decided to mount the horizontal stabilizer on the fuselage rather than the T-tail style of the Boeing 727. [14]

The initial assembly of the 737 was adjacent to Boeing Field (now officially called King County International Airport) because the factory in Renton was at capacity building the 707 and 727. After 271 aircraft, production was moved to Renton in late 1970. [13] [19] A significant portion of the fuselage assembly is in Wichita, Kansas previously by Boeing but now by Spirit AeroSystems , which purchased some of Boeing's assets in Wichita. [20] The fuselage is joined with the wings and landing gear, then moves down the assembly line for the engines, avionics and interiors. After rolling out the aircraft, Boeing tests the systems and engines before its maiden flight to Boeing Field, where it is painted and fine tuned before delivery to the customer. [21]

The first of six -100 prototypes rolled out in December 1966, and made its maiden flight on 9 April 1967 piloted by Brien Wygle and Lew Wallick. [22] During nearly 1,300 hours of flight testing it was discovered that the aircraft produced excess drag at high speeds, which could buckle the rear wing spar at loads only 34% above normal. The aircraft were modified with reinforcements, but at a cost to the weight and short-field performance. [23] On December 15, 1967 the Federal Aviation Administration certified the -100 for commercial flight, [24] issuing Type Certificate A16WE. [25] The 737 was the first aircraft to have, as part of its initial certification, approval for Category II approaches. [26] Lufthansa received their first aircraft on December 28, 1967 and on February 10, 1968 became the first non-American airline to launch a new Boeing aircraft. [24] Lufthansa was the only significant customer to purchase the 737-100 and only 30 aircraft were ever produced. [27]

The 737-200 had its maiden flight on August 8, 1967. It was certified by the FAA on December 21, 1967, [25] [28] and the inaugural flight for United was on April 28, 1968 from Chicago to Grand Rapids, Michigan. [24] The lengthened -200 was widely preferred over the -100 by airlines.

In 1968 an improvement to the thrust reversal system was introduced. The improvement became standard on all aircraft after March 1969, and a retrofit was provided for active aircraft. Boeing fixed the drag issue by introducing new longer nacelle/wing fairings, and improved the airflow over the flaps and slats. The production line also introduced an improvement to the flap system, allowing increased use during takeoff and landing. All these changes gave the aircraft a boost to payload and range, and improved the short-field performance. [24] In May 1971, after aircraft #135, all improvements, including more powerful engines and a greater fuel capacity, were incorporated into the 737-200, giving it a 15% increase in payload and range over the original -200s. [26] This became known as the 737-200 Advanced, which became the production standard in June 1971.

In 1970, Boeing received only 37 orders. Facing financial difficulties, Boeing considered closing the 737 production-line and selling the design to Japanese aviation companies. [13] After the cancellation of the Boeing Supersonic Transport, and the scaling back of 747 production, enough funds were freed up to continue the project. [29] In a bid to increase sales by offering a variety of options, Boeing offered a 737C (Convertible) model in both -100 and -200 lengths. This model featured a 340 cm × 221 cm (130 in × 87 in) freight door just behind the cockpit, and a strengthened floor with rollers which allowed for palletized cargo. A 737QC (Quick Change) version with palletized seating allowed for faster configuration changes between cargo and passenger flights. [30] With the improved short-field capabilities of the 737, Boeing offered the option on the -200 of the gravel kit, which enables this aircraft to operate on remote, unpaved runways. [31] [32] Until retiring its -200 fleet in 2007, Alaska Airlines used this option for some of its rural operations in Alaska. With the retirement of these aircraft, some airports, such as Red Dog Airport, have upgraded runway facilities from gravel to paved. [33] [34]

In 1988 the initial production run of the -200 model ended after producing 1,114 aircraft. The last one was delivered to Xiamen Airlines on August 8, 1988. [35] [36]

Improved Variants

Development began in 1979 for the 737's first major facelift. Boeing wanted to increase capacity and range, incorporating improvements to upgrade the aircraft to modern specifications, while also retaining commonality with previous 737 variants. In 1980 preliminary aircraft specifications of the variant, dubbed 737-300, were released at the Farnborough Airshow. [37]

The CFM56-3B-1 turbofan engine was chosen to power the aircraft, which yielded significant gains in fuel economy and a reduction in noise, but also posed an engineering challenge given the low ground clearance of the 737 and the larger diameter of the engine over the original Pratt and Whitney engines. Boeing and engine supplier CFMI solved the problem by placing the engine ahead of the wing, and by moving engine accessories to the sides of the engine pod, giving the engine a distinctive non-circular air intake. [38]

The passenger capacity of the aircraft was increased to 149 by extending the fuselage around the wing by 2.87 metres (9 ft 5 in). The wing incorporated a number of changes for improved aerodynamics. The wing tip was extended 9 in (23 cm), and the wing span by 1 ft 9 in (53 cm). The leading-edge slats and trailing-edge flaps were adjusted. [38] The flight deck was improved with the optional EFIS (Electronic Flight Instrumentation System), and the passenger cabin incorporated improvements similar to those developed on the Boeing 757. [39] The prototype -300, the 1,001st 737 built, first flew on 24 February 1984 with pilot Jim McRoberts. [39] It and two production aircraft flew a nine month long certification program. [40]

In June 1986 Boeing announced the development of the 737-400, [41] which stretched the fuselage a further 10 ft (3.0 m), increasing the passenger load to 170. [42] The -400s first flight was on February 19, 1988 and, after a seven-month/500-hour flight testing run, entered service with Piedmont Airlines that October. [43]

The -500 series was offered, due to customer demand, as a modern and direct replacement of the 737-200. It incorporated the improvements of the 737 Classic series; allowing longer routes with fewer passengers to be more economical than with the 737-300. The fuselage length of the -500 is 1 ft 7 in (48 cm) longer than the 737-200, accommodating up to 132 passengers. Both glass and older style mechanical cockpits arrangements were available. [43] Using the CFM56-3 engine also gave a 25% increase in fuel efficiency over the older -200s P&W engines. [43]

The 737-500 was launched in 1987 by Southwest Airlines, with an order for 20 aircraft, [44] and flew for the first time on June 30, 1989. [43] A single prototype flew 375 hours for the certification process, [43] and on February 28, 1990, Southwest Airlines received the first delivery. [45] The 737-500 has become a favorite of some Russian airlines, with Aeroflot-Nord, S7 Airlines, and Rossiya Airlines all buying second-hand models of the aircraft to replace aging Soviet -built aircraft.

After the introduction of the -600/700/800/900 series, the -300/400/500 series was called the 737 Classic series.

The price of jet fuel has skyrocketed in the past five years; airlines devote 40% of the retail price of an air ticket to pay for fuel in 2008, versus 15% in 2000. [46] Consequently, carriers have begun to retire the Classic 737 series to reduce their fleet sizes; replacements consist of more efficient Next Generation 737s or Airbus A320 /A319/A318 series aircraft. On June 4, 2008, United Airlines announced it would retire all 94 of its Classic 737 aircraft (64 737-300 and 30 737-500 aircraft), replacing them with Airbus A320 jets taken from its Ted subsidiary, which has been shut down. [47] [48] [49]

Next Generation

Prompted by the modern Airbus A320, Boeing initiated development of an updated series of aircraft in 1991. [50] After working with potential customers, the 737 Next Generation (NG) program was announced on November 17, 1993. [51] The 737NG encompasses the -600, -700, -800 and -900, and is to date the most significant upgrade of the airframe. The performance of the 737NG is essentially that of a new aircraft, but important commonality is retained from previous 737 models. The wing was modified, increasing its area by 25% and span by 16 ft (4.9 m), which increased the total fuel capacity by 30%. New, quieter, more fuel-efficient CFM56-7B engines were used. [52] All three improvements combined increase the 737's range by 900 NM, now permitting transcontinental service. [51] A flight test program was operated by 10 aircraft; 3 -600s, 4 -700s, and 3 -800s.

The first NG to roll out was a -700, on December 8, 1996. This aircraft, the 2,843rd 737 built, first flew on February 9, 1997. The prototype -800 rolled out on June 30, 1997 and first flew on July 31, 1997. The smallest of the new variants, the -600s, is the same size as the -500. It was the last in this series to launch, in December 1997. First flying January 22, 1998, it was given certification on August 18, 1998. [51] [53]

In 2004, Boeing offered a Short Field Performance package in response to the needs of Gol Transportes Aéreos, which frequently operates from restricted airports. The enhancements improve takeoff and landing performance. The optional package is available for the 737NG models and standard equipment for the 737-900ER.

Boeing has already hinted that a "clean sheet" replacement for the 737 (internally dubbed " Boeing Y1") could follow the Boeing 787. [54]

Design

Engines on the 737 Classic series (300, 400, 500) and Next-Generation series (600, 700, 800, 900) appear not to have circular inlets, as most aircraft do. The accessory gearbox was moved from the 6 o'clock position under the engine to the 4 o'clock position (forward looking aft). This was done because the 737 sits lower to the ground than most airliners and the original 737s were designed for small P&W engines, but additional ground clearance was needed for the larger CFM56 engines. This side-mounted gearbox gives the engine a somewhat triangular rounded shape. Because the engine is close to the ground, 737-300s and later are more prone to engine foreign-object damage (FOD).

737s are not equipped with fuel dump systems. Depending upon the nature of the emergency, 737s either circle to burn off fuel or land overweight. To save weight and reduce cost and complexity the 737 lacks full doors to cover the main landing gear. The main landing gear (under the wings at mid-cabin) rotate into wells in the aircraft's belly, the legs being covered by partial doors, and "brush-like" seals aerodynamically smooth (or "fair") the wheels in the wells. The sides of the tires are exposed to the air in flight. "Hub caps" complete the aerodynamic profile of the wheels. It is forbidden to operate without the caps, because they are linked to the ground speed sensor that interfaces with the anti-skid brake system. When observing a 737 takeoff, or at low altitude, the dark circles of the tires can be plainly seen.

The primary flight controls are intrinsically safe. In the event of total hydraulic system failure or double engine failure, they will automatically and seamlessly revert to control via servo tab. The 737 is the only modern passenger aircraft this size or larger that can operate completely without hydraulics.

Most 737 cockpits are equipped with "eyebrow windows" positioned above the main glareshield. Eyebrow windows were a feature of the original 707. They allowed for greater visibility in turns, and offered better sky views if navigating by stars. With modern avionics, they became redundant, and many pilots actually placed newspapers or other objects in them to block out sun glare. They were eliminated from the 737 cockpit design in 2004, although they are still installed in military variants and at customer request. These windows are sometimes removed and plugged, usually during maintenance overhauls and can be distinguished by a metal plug which differs from smooth metal which appears in later aircraft that were not originally fitted with the windows.

Blended winglets are available as retrofits and in production on newer 737 aircraft. These winglets stand approximately 8 feet (2.4 m) tall and are installed at the wing tips. They help with reduced fuel burn (by reducing vortex drag), reduced engine wear, and less noise on takeoff.

A short-field design package is available for the 737-600, -700 and -800, allowing operators to fly increased payload to and from airports with runways under 5,000 feet (1,500 m). The package consists of sealed leading edge slats (improved lift), a two-position tail skid (enabling reduced approach speeds) and increased flight spoiler deflection on the ground. These improvements are standard on the 737-900ER. [55]

Variants

The 737 models can be divided into three generations, including nine major variants. The "Original" models consist of the 737-100, 737-200/-200 Advanced. The "Classic" models consist of the 737-300, 737-400, and 737-500. The "Next Generation" variants consist of the 737-600, 737-700/-700ER, 737-800, and 737-900/-900ER. Of these nine variants, many feature additional versions such as the T-43, which is a modified Boeing 737-200 used by the United States Air Force (USAF)

737 Original

737-100

The initial model was the 737-100 . It was launched by Lufthansa in 1965. The -100 was rolled out on January 17, 1967 and entered service in 1968. The aircraft is the smallest variant of the 737. Only 30 737-100s were ordered and delivered, and no 737-100s remain in service today. The original Boeing prototype, last operated by NASA, retired more than 30 years after its maiden flight, and is on exhibit in the Museum of Flight in Seattle. [51]

737-200

The 737-200 is a 737-100 with an extended fuselage. It was launched by United Airlines in 1965. The -200 was rolled out on June 29, 1967 and entered service in 1968. The 737-200 Advanced is an improved version of the -200, introduced by All Nippon Airways on May 20, 1971. [56] The aircraft has improved aerodynamics, automatic wheel brakes, more powerful engines, more fuel capacity and longer range than the -200. [57] Boeing also provided the 737-200C (Convertible), that allowed conversion between passenger and cargo use and the 737-200QC (Quick Change), facilitating rapid conversion between roles. The last delivery of a -200 series aircraft was in August 1988. [58] A large number of 737-200s are still in service, mostly with "second tier" airlines and those of developing nations. They are being phased out because of poor fuel efficiency, high noise emissions (despite the vast majority having had their JT8Ds fitted with hush kits) and escalating maintenance costs. Some regions have gone as far as to ban them. [citation needed] This airliner is able to operate on gravel runways with a gravelkit installed. Gravel kitted 737-200 Combis are currently used by Canadian North, First Air in northern Canada, and Cayman Airways. For many years, Alaska Airlines, also made use of them.

Nineteen 737-200s were converted to be used to train aircraft navigators for the U.S. Air Force, designated T-43. Some were modified into CT-43s which are used to transport passengers and one was modified as the NT-43A Radar Test Bed. The first one was delivered on July 31, 1973 and the last on July 19, 1974. The Indonesian Air Force ordered three modified 737-200s, designated Boeing 737-2x9 Surveiller. They were used as Maritime reconnaissance (MPA)/transport aircraft, fitted with SLAMMAR (Side-looking Multi-mission Airborne Radar). The aircraft were delivered between May 1982 and October 1983. [59]

After 40 years, the final 737-200 aircraft in the United States flying scheduled passenger service were phased out on March 31, 2008 with the last flights of Aloha Airlines (Aloha continues to fly its interisland cargo flights). The aircraft had been eliminated from regular service in the continental United States in 2006, when Delta Air Lines withdrew the type. [citation needed]

737 Classic

The new 737 Classic series featured CFM56 turbofan engines, which yielded significant gains in fuel economy and a reduction in noise, but also posed an engineering challenge given the low ground clearance of the 737. Boeing and engine supplier CFMI solved the problem by placing the engine ahead of (rather than below) the wing, and by moving engine accessories to the sides (rather than the bottom) of the engine pod, giving the 737 a distinctive non-circular air intake. [60] The wing incorporated a number of changes for improved aerodynamics.

737-300

The 737-300 was launched in 1981 by both USAir and Southwest Airlines becoming the first model of the 737 Classic series. The aircraft has a typical capacity of 128 passengers in a two class configuration (137 seats in a one class coach seating configuration). [61] The 300 series remained in production until 1999 when the last aircraft was delivered to Air New Zealand on December 17, 1999.

Various modifications have been made to aircraft previously in service. The 737-300 can be retrofitted with Aviation Partners Boeing winglets. The 737-300 retrofitted with winglets is designated the -300SP (special performance). Used passenger -300 aircraft have also been converted to freighter versions. The Lockheed Martin CATBird is a modified 737-300 with the nose of a Lockheed F-35 Lightning II, a pair of canards, and (inside) an F-35 cockpit; to be used to flight test the F-35's complete avionics suite.

In December 2008, Southwest Airlines selected Boeing to retrofit its 737-300s with new avionics, in order to improve commonality with its 737-700s, as well as to support the Required Navigation Performance initiative. [62]

737-400

The 737-400 was launched in 1985 as a stretched 737-300, primarily for use by charter airlines. Piedmont Airlines was the launch customer with an order for 25 aircraft in 1986. [63] The first 400 entered service in 1988 with Piedmont. The last delivery of the -400 occurred on February 25, 2000 to CSA Czech Airline. [58]

The 737-400F was not a model delivered by Boeing but a converted 737-400 to an all cargo aircraft. Alaska Airlines was the first to convert one of its 400s from regular service to an aircraft with the ability to handle 10 pallets. [64] The airline has also converted five more into fixed combi aircraft for half passenger and freight. These 737-400 Combi aircraft are now in service.

737-500

The 737-500 was launched in 1987 by Southwest Airlines and entered service in 1990. The fuselage length of the 737-500 is similar to the 737-200 while incorporating the improvements of the 737 Classic series. It offered a modern and direct replacement of the 737-200, while also allowing longer routes with fewer passengers to be more economical than with the 737-300. The last -500 was delivered to All Nippon Airlines on July 26, 1999. [58]

The 737-500 has become a favorite of some Russian airlines, with Aeroflot-Nord , Rossiya Airlines, S7 Airlines, Sky Express, Transaero, and Yamal Airlines all buying second-hand models of the aircraft to replace aging Soviet -built aircraft and/or expand their fleets. Also Aerolineas Argentinas is replacing the 737-200 with second-hand 737-500.

737 Next Generation

By the early 1990s, it became clear that the new Airbus A320 was a serious threat to Boeing's market share, as Airbus won previously loyal 737 customers such as Lufthansa and United Airlines. In November 1993, Boeing's board of directors authorized the Next Generation program to replace the 737 Classic series. The -600, -700, and -800 series were planned. [65] After engineering trade studies and discussions with major 737 customers, Boeing proceeded to launch the 737 Next Generation series.

Passenger cabin improvements similar to those on the Boeing 777, featuring more curved surfaces and larger overhead bins than previous generation 737s. The Next Generation 737 interior was also adopted on the Boeing 757-300 .

New airfoil section, increased wing span, area, and chord

Winglets on most models

Redesigned vertical stabilizer

(As of July 2008) Carbon brakes manufactured by Messier-Bugatti. These new brakes, now certified by the Federal Aviation Administration, weigh 550–700 lb (250–320 kg) less than the steel brakes normally fitted to the Next-Gen 737s (weight savings depend on whether standard or high-capacity brakes are fitted). [67] A weight reduction of 700 pounds on a Boeing 737-800 results in 0.5% reduction in fuel burn. [68]

Boeing delivered the 5,000th 737 to Southwest Airlines on February 13, 2006. Boeing delivered the 6,000th 737 to Norwegian Air Shuttle in April 2009.

737-600

The 737-600 replaced the 737-500 in Boeing's line up, and was also intended to replace airlines' DC-9s. The 737-600 was launched by Scandinavian Airlines System in 1995 with the first aircraft delivered on September 18, 1998. The -600 is the only Boeing 737 still in production that does not include winglets as an option. [69] WestJet was to be the Boeing launch customer for the 737-600 with winglets, but announced in their Q2 2006 results that they were not going to move ahead with those plans.

The 737-600 competes with the Airbus A318, Embraer 195, and the upcoming Bombardier CSeries jet. [70] [71] A total of 69 -600s have been delivered with no unfilled orders as of 2009. [6]

737-700

The 737-700 was the first of Next Generation series when launch customer Southwest Airlines ordered the variant in November 1993. The variant was based on the 737-300 and entered service in 1998. [72] It replaced the 737-300 in Boeing's lineup, and its direct competitor is the A319. It typically seats 132 passengers in a two class cabin or 149 in all economy configuration.

The 737-700C is a convertible version where the seats can be removed from the aircraft to carry cargo. There is a large door on the left side of the aircraft. The US Navy was the launch customer for the 737-700C. [73]

Boeing launched the 737-700ER on 31 January 2006. [74] All Nippon Airways is the launch customer, with the first one delivered on February 16, 2007. The 737-700ER is a mainline passenger version of the BBJ1 and 737-700IGW. It combines the 737-700 fuselage with the wings and landing gear of a 737-800. It will offer a range of 5,510 nautical miles (10,205 kilometers), with seating for 126 passengers in a traditional 2-class configuration. A competitor to this model would be the A319LR. The 700ER has the longest range for a 737.

At the end of July 2008, Delta Air Lines took delivery of the first of 10 -700 model aircraft fitted with Messier-Bugatti's carbon brakes. [75]

All Nippon Airways, Japan's second-biggest carrier, is to pioneer the model in Asia with a daily service between Tokyo and Mumbai. ANA's service, believed to be the first all-business class route connecting to a developing country, was to start in September 2007 and use a Boeing 737-700ER outfitted with 36 seats and an extra fuel tank. [76]

The C-40A Clipper is a 737-700C used by the U.S. Navy as a replacement for the C-9B Skytrain II. The C-40B and C-40C are used by the US Air Force for transport of Generals and other senior leaders. The Boeing 737 AEW&C is a 737-700IGW roughly similar to the 737-700ER. This is an Airborne Early Warning and Control (AEW&C) version of the 737NG. Australia is the first customer (as Project Wedgetail), followed by Turkey and South Korea.

737-800

The 737-800 is a stretched version of the 737-700, and replaces the 737-400. It also filled the gap left by Boeing's discontinuation of the McDonnell Douglas MD-80 and MD-90 after Boeing's merger with McDonnell Douglas. The -800 was launched by Hapag-Lloyd Flug (now TUIfly) in 1994 and entered service in 1998. The 737-800 seats 162 passengers in a two class layout, or 189 in one class, and competes with the A320. For many airlines in the U.S., the 737-800 replaced aging Boeing 727-200 trijets and MD-80 series and MD-90 aircraft.

The P-8 Poseidon is a 737-800ERX ("Extended Range") that, on June 14, 2004, Boeing's Integrated Defense Systems division beat Lockheed Martin in the contest to replace the P-3 Orion maritime patrol aircraft. Eventual orders may exceed 100 from the US Navy. The P-8 is unique in that it has 767-400ER -style raked wingtips, instead of the blended winglets available on other 737NG variants.

737-900

Boeing later introduced the 737-900, the longest and most powerful variant to date. Alaska Airlines launched the 737-900 in 1997 and accepted delivery on May 15, 2001. Because the -900 retains the same exit configuration of the -800, seating capacity is limited to 177 seats in two classes, or 189 in a single-class layout. The 737-900 also retains the MTOW and fuel capacity of the -800, trading range for payload. These shortcomings until recently prevented the 737-900 from effectively competing with the Airbus A321 .

The 737-900ER , which was called the 737-900X prior to launch, is the newest addition and the largest variant of the Boeing 737 line and was introduced to meet the range and passenger capacity of the discontinued 757-200 and to directly compete with the Airbus A321.

An additional pair of exit doors and a flat rear pressure bulkhead increase seating capacity to 180 passengers in a 2-class configuration or 215 passengers in a single-class layout. Additional fuel capacity and standard winglets improve range to that of other 737NG variants.

The first 737-900ER was rolled out of the Renton, Washington factory on August 8, 2006 for its launch customer, Lion Air. Lion Air received this aircraft on April 27, 2007 in a special dual paint scheme combining the Lion Air lion on the vertical stabilizer and the Boeing livery colors on the fuselage.

The 737-900ER is now the standard 737-900 model offered by Boeing. The 737-900 non-ER model has been discontinued in favor of the -900ER.

Boeing Business Jet

Plans for a business jet version of the 737 are not new. In the late 1980s, Boeing marketed the 77-33 jet, a business jet version of the 737-300. [77] The name was short-lived. After the introduction of the next generation series, Boeing introduced the Boeing Business Jet (BBJ) series. The BBJ1 was similar in dimensions to the 737-700 but had additional features, including stronger wings and landing gear from the 737-800, and has increased range (through the use of extra fuel tanks) over the other 737 models. The first BBJ rolled out on 11 August 1998 and flew for the first time on September 4. [ 8]

On October 11, 1999 Boeing launched the BBJ2. Based on the 737-800, it is 5.84 metres (19 ft 2 in) longer than the BBJ, with 25% more cabin space and twice the baggage space, but has slightly reduced range. It is also fitted with auxiliary belly fuel tanks and winglets. The first BBJ2 was delivered on 28 February 2001. [78]

Boeing's BBJ3 is based on the 737-900ER. The BBJ3 has 1,120 square feet (104 m 2 ) of floor space, 35% more interior space and 89% more luggage space than the BBJ2. It has an auxiliary fuel system, giving it a range of up to 4,725 nautical miles (8,751 km), and a Head-up display . Boeing completed the first example in August, 2008. This aircraft's cabin is pressurized to a simulated 6,500-foot (2,000 m) altitude. [79]

Operators

The 737 is operated by more than 500 airlines, flying to 1,200 destinations in 190 countries. With over 8,000 aircraft ordered, over 6,000 delivered, and over 4,500 still in service, at any given time there are on average 1,250 airborne worldwide. On average, somewhere in the world, a 737 takes off or lands every five seconds. [7] Since entering service in 1968, the 737 has carried over 12 billion passengers over 120 billion km (65 billion nm), and has accumulated more than 296 million hours in the air. The 737 represents more than 25% of the worldwide fleet of large commercial jet airliners. [7] [80]

Military

Many countries operate the 737 passenger and cargo variants in government or military applications.

Abu Dhabi

1 - Abu Dhabi Amiri Flight

Australia

2 leased jets for VIP transport and operated by Royal Australian Air Force

Brazil

2 - Brazilian Air Force for VIP transport

Chile

2 - Chilean Air Force for VIP transport

Colombia

1 - Colombian Air Force for VIP transport

Dubai

1 - Dubai Air Wing/Royal Flight (BBJ)

Equatorial Guinea

1 - Equatorial Guinea Government (BBJ)

India

3 - Indian Air Force for VIP transport

Indonesia

4 - Indonesian National Air Force - 1 for VIP transport and 3 for maritime reconnaissance